Cylinder-to-cylinder variations in diesel dual fuel combustion under low-load conditions

Abstract

Diesel dual-fuel (DDF) operation is a promising alternative engine operating mode. DDF combustion can achieve lower soot and NOx emissions compared to conventional diesel engine operations. However, DDF engine operations suffer from high HC (mainly CH4) emissions and poor engine operating stability, especially under low load conditions. The current study investigated cylinder-to-cylinder variations in the DDF combustion in a four-cylinder turbocharged direct-injection diesel engine. All experiments were performed under steady-state engine conditions at 1800 rpm for a range of diesel injection timings and EGR rates.

Data showed that the diesel injection timing and the EGR played an important role in controlling both cyclic variation and cylinder variation in the cylinder outputs. High %EGR was needed to achieve stable DDF combustion in all cylinders. Several factors could render cylinder-to-cylinder variation in the combustion and the combustion stability in each cylinder including the mixture lambda, the EGR distribution, the thermal stratification in the intake, and the charge inhomogeneities. As the cylinder-to-cylinder variation in the combustion became small, the engine efficiency together with HC and CO emissions can be reduced.